1. Field of the Invention
The present invention relates to the drilling and remedial operations associated with offshore oil or gas wells, and the like. More particularly, the present invention relates to a method and apparatus for the transfer of a drilling apparatus from a movable vessel such as a jack-up rig to a permanent fixed offshore structure, where the transfer is effected by raising the movable vessel and contained drilling apparatus to the appropriate level adjacent the fixed structure and skidding the drilling apparatus onto the permanent fixed platform structure.
2. Prior Art
In the drilling of offshore oil wells, a fixed platform is constructed above a promising field, whereafter several wells may be drilled from the platform for the eventual production of oil or natural gas.
In an economic decision, the drilling portion of the platform is removed after the necessary wells have been drilled. When the drilling structure is removed, the platform becomes merely a production platform, no longer having "drilling" capabilities. After a time, the situation can develop where a drilling structure is needed on the platform once again. Sometimes additional wells may be desired in a field which was not productive economically in years previous. A raise in the price of oil can change the economic situation, making prior fields which were not economically feasible now attractive to the owner or lessee. This can bring about the need for drilling new wells off of an existing fixed platform. Additionally, existing wells may require remedial operations which necessitate the use of a drilling type structure. In either case, it is a costly and time consuming problem to replace the drilling structure once again on the fixed platform after it was previously removed.
The present method for placing or replacing a drilling apparatus and its associated substructure onto a platform is by the use of an enormous derrick mounted on a conventional type barge. This vessel is known in the oil and gas offshore industry as a "derrick barge". Several derrick barges are operating in this country, and the cost is estimated to be about $50,000.00 a day. Additionally, the time to install the oil drilling apparatus and its associated substructure back onto the fixed platform is usually a minimum of 4 days. Not only is there the cost of the rental on a derrick barge for 4 days, but this method ties up 4 days of time which normally would be available to drill for oil, which revenues are additionally lost.